This invention relates generally to door locks, and more particularly to a security door lock which is especially designed to withstand attempts to force it open.
Ordinary doors can be kicked, pried or forced open, the portion of the jamb near a dead bolt being broken by the force. One approach to this problem is to build up or otherwise strengthen the jamb adjacent the bolt plate. Another approach, disclosed in U.S. Pat. Nos. 915,397 and 4,294,040, is to spread the force over the entire jamb or over the entire door frame.
U.S. Pat. No. 915,397 discloses a vault door movable by sliding and swinging. The door can be manually swung open and closed. When the door is closed, the outer edge of the vault door is slidable laterally into a vertical channel in the door jamb to protect against the door being blown open. The door is locked by rotation of a hand wheel, which turns a screw to drive two levers, thereby pushing the door (on pivot balls) into the channel in the door jamb. When the door slides into the channel, projections on the top and bottom of the door engage ribs on the top and bottom of the door frame, a bolt engages the inner edge of the door, and projections on the inner edge of the door enter recesses in the door jamb. However, this door is heavy and unwieldy to open and close, making it unsuitable for residential and many commercial buildings.
U.S. Pat. No. 4,294,040 discloses a two-part safety door for buildings and rooms which is intended for use in residential houses. The door comprises a door body and a supporting column, slidable from an unsecured position to a secured position wherein the outer vertical edge of the door body is received in a cavity in the jamb. The door can be locked in the secured position by vertical latches. When a handle is pulled, the door body and the supporting column slide on guides. In its unsecured position, the door body can rotate on hinges attached to the supporting column. Since both the door and the supporting column must be manually slid to secure this door, this door is unwieldy for many people and uses. In addition, the door and supporting column must be manually slid to the unsecured position.
U.S. Pat. No. 4,679,353, co-invented by the same inventors of this invention, discloses a security door which is capable of withstanding kicking or prying without breaking open and which may be easily opened by those, including handicapped people or children, who are authorized to do so. Means are provided so that the door may be shifted to its secured position without requiring the user to pull or push the door. Means are also provided for returning the door to its unsecured position when the door is unlocked. In addition to a secured position within the jamb, the door is capable of being latched or locked in the closed (but unsecured) position in the same way that a conventional door is locked. In particular, the security door comprises first and second vertical door jambs spaced from one another to define a doorway therebetween, and a door for closing the doorway. The second door jamb has a generally channel-shaped recess therein extending generally vertically from adjacent the bottom of the jamb to adjacent the top of the jamb. The security door includes a hinge on the first door jamb for supporting the door adjacent one vertical edge of the door, constituting its inner edge. The hinge enables the door to swing on a generally vertical axis between an open position wherein the door is swung out of the doorway and a closed position wherein the door closes the doorway and the opposite vertical edge of the door, constituting its outer edge, is spaced inwardly from the recess in the second door jamb. The door is movable outwardly in the plane of the doorway from its closed position to a secured position wherein the outer vertical edge is received in the vertical recess thereby to prevent the door from swinging out of its secured position. The security door further includes springs for urging the door away from its secured position and locking apparatus operable to pull the outer vertical edge of the door into the vertical recess and to maintain the door in its secured position against the urging of the springs. The locking apparatus comprises cooperable locking components in the door and the second door jamb. While the design and operation of this door are generally satisfactory, a special door jamb is required. Moreover a conventional door cannot readily be adapted to incorporate the features of the invention.
Accordingly, there is a need for a security lock which can be used to secure a door against kicking or prying without breaking open, and which is especially adapted to be fitted on conventional doors without undue effort.